Preparation and gas sensitivity of WO3 hollow microspheres and SnO2 doped heterojunction sensors

Dispersed tungsten trioxide (WO3) microsphere aggregates were prepared by chemical reduction with hydrazine hydrate in a glycol-water system, and the composites of WO3/tin oxide (SnO2) with different SnO2 weight fractions were prepared by microwave refluxing. The products were characterized by x-ray diffraction, field emission scanning electron microscopy, thermogravimetric-differential thermal analysis, Fourier transform infrared spectroscopy, and the Brunauer-Emmett-Teller method. The gas-sensing characteristics based on the composites were investigated by a stationary-state gas distribution method. The results show that the noncompact WO3 microspheres with hollow structure were obtained. The phase composition and the morphology of WO3 were changed by SnO2 doping. The heterojunction structure was formed between WO3 and SnO2, and the heterojunction sensors have high sensitivity to H2S, NOX, and xylene at relatively lower operating temperature, especially the sensor doped by 3% SnO2 operating just at 90 °C for H2S gas.